US20070063192A1 - Systems for emitting light incorporating pixel structures of organic light-emitting diodes - Google Patents

Abstract

Systems for emitting light incorporating pixel structures of organic light-emitting diodes (OLEDs) are provided. A representative system comprises: a first sub-pixel area including a first OLED; and a second sub-pixel area including a second OLED and a second control circuit, wherein said second control circuit includes electronic components for controlling said first and second OLEDs.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates to organic light-emitting diodes (OLEDs).
• 2. Description of the Related Art
• An organic light-emitting diode (OLED) display is a flat display capable of emitting a light in which an organic compound is employed as a lighting material. An OLED display may provide advantages of compactness, slightness, a wide viewing angle, a high contrast, and a high response speed, among others.
• Referring toFIG. 1, a sub-pixel of a conventional OLED display is schematically depicted. The OLED display comprises a plurality of pixels, each comprising a plurality ofsub-pixel areas11. Apower line12, adata line13 and ascan line14 are shown. Thesub-pixel area11 includes a light-emitting area15 and a non-light-emitting area16.
• The light-emittingarea15 comprises an OLED formed with an organic compound film through which electrical energy (provided by the power line) is transformed into light energy. he non-light-emitting area16 has a control circuit (not shown) for controlling the OLED in the light-emitting area15.
• The control circuit typically comprises diodes, transistors, capacitors and other electronic components. Since the non-light-emitting area16 does not emit any light, it is desired to have a smaller area thereof. The ratio of the area of the light-emittingarea15 to the area of thesub-pixel area11 is called the “aperture ratio.” Thus, a higher aperture ratio corresponds to higher luminance.
• Referring toFIG. 2A, a prior pixel structure of a typical full-color OLED display is schematically depicted. In the full-color OLED display, each pixel comprises ared sub-pixel area17, agreen sub-pixel area18 and ablue sub-pixel area19. In thered sub-pixel area17, a light-emitting area20 has an R-OLED and a non-light-emitting area21 has a control circuit for the R-OLED. In the green andblue sub-pixel areas18,19, similar structures as that set forth in thered sub-pixel area17 are provided.
• By virtue of the control circuits of thesub-pixel areas17,18,19, the luminance of the OLEDs may be controlled to achieve full color image display. Since light emission efficiency of the presently available red, green, and blue OLEDs is not identical and since the light-emitting areas corresponding thereto are generally the same, the OLED of poorer light emission efficiency has to be supplied with larger electric energy so as to have the same luminance as that of the other OLEDs.
• Referring toFIG. 2B, another prior pixel structure of a typical full-color OLED display is schematically depicted. In this full-color OLED display, each pixel comprises ared sub-pixel area22, agreen sub-pixel area23, ablue sub-pixel area24 and awhite sub-pixel area25. In thewhite sub-pixel area25, a light-emitting area26 has a W-OLED and a non-light-emitting area27 has a control circuit for the W-OLED.
• InFIG. 2A, if a white image is desired to be displayed, illumination from red, green, andblue sub-pixels17,18, and19 should be combined. However, inFIG. 2B, if a white image is desired to be displayed, only thewhite sub-pixel25 is required to emit that is, the red, green, andblue sub-pixels22,23, and24 need not emit. Therefore, the RGBW OLED display ofFIG. 2B typically requires less power consumption than the RGB OLED display ofFIG. 2A when a white image is displayed. However, since the control circuits in the non-light-emitting areas must accommodate a fixed area, the RGBW OLED display ofFIG. 2B suffers from having smaller light-emitting area, that is, a lower aperture ratio than the aperture ratio of the RGB OLED display ofFIG. 2A.
SUMMARY OF THE INVENTION
• The present invention provides systems for emitting light. An embodiment of such a system comprises a pixel structure of an organic light-emitting diode (OLED). The pixel structure comprises: a first sub-pixel area including a first OLED; and a second sub-pixel area including a second OLED and a second control circuit, wherein said second control circuit includes electronic components for controlling said first and second OLEDs.
• In another embodiment of such a system, the pixel structure of an organic light-emitting diode (OLED) comprises a blue sub-pixel area including a blue OLED, and a white sub-pixel area including a white OLED and a second control circuit. The second control circuit includes electronic components for controlling the blue and white OLEDs. The blue sub-pixel area can include no electronic components.
BRIEF DESCRIPTION OF THE DRAWINGS
• The invention will become more fully understood from the detailed description given below for illustration only. The embodiments described are not limitative of the present invention. In the drawings:
• FIG. 1 illustrates schematically a prior sub-pixel structure of organic light-emitting diode (OLED) display;
• FIG. 2A illustrates schematically a prior pixel structure of a full-color organic light-emitting diode (OLED) display;
• FIG. 2B illustrates schematically another prior pixel structure of a full-color organic light-emitting diode (OLED) display;
• FIG. 3 illustrates schematically a pixel structure of a first of embodiment an OLED display;
• FIG. 4 illustrates schematically an embodiment of a control circuit for a pixel structure of an OLED display;
• FIG. 5 illustrates schematically a pixel structure of a second embodiment of an OLED display;
• FIG. 6 illustrates schematically the control circuit for pixel structure of the OLED display ofFIG. 5;
• FIG. 7 illustrates schematically a third embodiment of a pixel structure of OLED display.
• FIG. 8 illustrates schematically an embodiment of a display device; and
• FIG. 9 illustrates schematically an embodiment of an electronic device.
DETAILED DESCRIPTION
• Referring toFIG. 3, a first embodiment of a pixel structure of an organic light-emitting diode (OLED) display-is depicted schematically. Thepixel structure3 of the OLED display comprises: afirst sub-pixel area31 and asecond sub-pixel area32. Thefirst sub-pixel area31 includes afirst OLED33, but does not include a control circuit. Thesecond sub-pixel area32 includes asecond OLED34 and acontrol circuit35. Thecontrol circuit35 includes a firstcontrol circuit portion35a, and a secondcontrol circuit portion35b. The firstcontrol circuit portion35aincludes electronic components for controlling thefirst OLED33, and the secondcontrol circuit portion35bincludes electronic components for controlling thesecond OLED34.
• In this embodiment, the light emission efficiency of thefirst OLED33 can be lower than that of thesecond OLED34. For example, thefirst OLED33 can be a blue OLED and thesecond OLED34 can be a red, green or white OLED. Since the firstcontrol circuit portion35afor controlling thefirst OLED33 is disposed in thesecond sub-pixel area32, but not in thefirst sub-pixel area31, the area of thefirst OLED33 may be increased as compared to that used in the prior art. This potentially enables brightness and lifetime of thefirst OLED33 resident in thefirst sub-pixel area31 to be improved.
• Referring toFIG. 4, a first embodiment of acontrol circuit35 for thepixel3 of the OLED display is depicted schematically. As mentioned above, both of thecontrol circuit portions35aand35bare disposed in thesecond sub-pixel area32. The firstcontrol circuit portion35acomprises afirst switch transistor41, afirst capacitor43, and afirst driving transistor45 that are used for controlling thefirst OLED33. The secondcontrol circuit portion35bcomprises asecond switch transistor42, asecond capacitor44, and asecond driving transistor46, that which are used for controlling thesecond OLED34.
• When a signal Vscan1 on a scan line is transmitted to the gate of thefirst switch transistor41, a signal Vdata1 on a data line is taken and stored in thefirst capacitor43 through thefirst switch transistor41 and turns on thefirst driving transistor45. Thefirst driving transistor45 is connected to a power line having a voltage level of Vdd1 and thefirst OLED33, and thereby provides a driving current to thefirst OLED33. Thefirst OLED33 is also connected to a voltage level Vss1 and receives the driving current. Once the driving current is being received, electric energy provided by the power line is transformed into light energy. With regard to the transistors mentioned above, amorphous Si (a-Si) thin film transistors (TFTs), high temperature poly-silicon TFTs, low temperature poly-silicon TFTs and single crystal silicon TFTs may be used. Thefirst switch transistor41, thefirst capacitor43 and thefirst driving transistor45 are disposed in thesecond sub-pixel area32 to increase the area of thefirst OLED33 as compared to that in the prior art. Therefore, brightness and lifetime of theOLED33 in thefirst sub-pixel area31 are can be improved.
• Referring toFIG. 5, a second embodiment of a pixel structure of an OLED display is depicted. Thepixel structure5 of the OLED display comprises afirst sub-pixel area51 and asecond sub-pixel area52. Thefirst sub-pixel area51 comprises afirst OLED53 and afirst control circuit55 having electronic components for controlling thefirst OLED53. Thesecond sub-pixel area52 comprises asecond OLED54 and asecond control circuit56. Thesecond control circuit56 includes at least one electronic component for controlling thefirst OLED53 and at least one electronic component for controlling thesecond OLED54. For example, thesecond control circuit56 disposed in thesecond sub-pixel area52 comprises a firstcontrol circuit portion56afor controlling thefirst OLED53 and a secondcontrol circuit portion56bfor controlling thesecond OLED54. In this embodiment, the light emission efficiency of thefirst OLED53 can be lower than that of thesecond OLED54. For example, thefirst OLED53 can be a blue OLED and thesecond OLED54 can be a red, green or white OLED. At least one of the electronic components for controlling thefirst OLED53 is disposed in thesecond sub-pixel area52. Thus, the area of thefirst OLED53 can be increased compared to the conventional OLED. Therefore, brightness and lifetime of thefirst OLED53 can be improved.
• Referring toFIG. 6, the control circuits for thepixel5 of the OLED display are depicted in greater detail. Thefirst control circuit55 comprises afirst switch transistor61. Thesecond control circuit56 comprises a firstcontrol circuit portion56aincluding afirst capacitor63 and afirst driving transistor65, and a secondcontrol circuit portion56bincluding asecond switch transistor62, asecond capacitor64 and asecond driving transistor66. Thefirst control circuit55 and the firstcontrol circuit portion56aare used for controlling thefirst OLED53. The secondcontrol circuit portion56bis used for controlling thesecond OLED54.
• Referring toFIG. 7, a third embodiment of a pixel structure of an OLED display is depicted. Thepixel structure7 of the OLED display comprises anR sub-pixel area71, aG sub-pixel area72, aB sub-pixel area73, and aW sub-pixel area74. TheR sub-pixel area71 includes an R-OLED711 and acontrol circuit712. TheG sub-pixel area72 includes a G-OLED721 and acontrol circuit722. TheB sub-pixel area73 includes a B-OLED731 and acontrol circuit732. TheW sub-pixel area74 includes a W-OLED741 and acontrol circuit742.
• According to this embodiment, thecontrol circuit712 includes all the electronic components, including a switch transistor, a driving transistor and a capacitor, for controlling the R-OLED711. Thecontrol circuit722 includes all the electronic components, including a switch transistor, a driving transistor and a capacitor, for controlling the G-OLED721. However, thecontrol circuit732 only includes a portion of the electronic components for controlling the B-OLED731. The other electronic components for controlling the B-OLED731 are disposed in theW sub-pixel area74. For example, as shown inFIG. 7, only one transistor for controlling the B-OLED731 is disposed in theB sub-pixel area73, while a transistor and a capacitor for controlling the B-OLED731 are disposed in theW sub-pixel area74. Thus, theW sub-pixel area74 includes thecontrol circuit742 for controlling both the B-OLED731 and the W-OLED741.
• Thus, thecontrol circuit732 disposed in theB sub-pixel area73 accomodates the smallest area, and thecontrol circuit742 disposed in theW sub-pixel area74 accomodates the largest area, among the four color sub-pixel areas. Generally, white OLED has the highest light emitting efficiency, and blue the lowest light emitting efficiency among the four color OLED materials. Therefore, by re-arrangment of the electronic components for controlling the B-OLED, e.g. disposing the electronic components for controlling the B-OLED in the white sub-pixel area, the B-OLED area is increased and the W-OLED area is decreased. Thus, the total light emitting efficiency of the B-OLED in the B sub-pixel area and the total light emitting efficiency of the W-OLED in the W sub-pixel area can be optimally adjusted.
• FIG. 8 shows an embodiment of a system implemented as adisplay device80.Display device80 comprises adisplay panel81 incorporating a pixel structure, such as thepixel structure7 as shown inFIG. 7. Thedisplay panel81 can be coupled to acontroller82. Thecontroller82 can comprise source and gate driving circuits (not shown), controlling thedisplay panel81 for operation of thedisplay device80.
• FIG. 9 is a schematic diagram illustrating an embodiment of a system implemented as anelectronic device90.Electronic device90 incorporates a display device, such as thedisplay device80 shown inFIG. 8. Aninput91 is coupled to thecontroller82 of thedisplay device80. Theinput91 can include a processor or the like to input image data to thecontroller82 to render an image. Theelectronic device90 may be a portable device such as a PDA, notebook computer, tablet computer, cellular phone, or a display monitor device, or a non-portable device such as a desktop computer, for example.
• In conclusion, some embodiment of the present invention dispose the electrical components for controlling B-OLEDs to W sub-pixel areas. Thus, the area of a B-OLED, which has low light emitting efficiency, can be increased. Therefore, the total light emitting efficiency of the B-OLED in the B sub-pixel area can be increased.
• While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts herein.

Claims (20)

1. A system for emitting light comprising:

a pixel structure of an organic light-emitting diode (OLED), the pixel structure comprising:

a first sub-pixel area including a first OLED; and

a second sub-pixel area including a second OLED and a second control circuit, wherein said second control circuit includes electronic components for controlling said first and second OLEDs.

2. The system as claimed inclaim 1, wherein the first sub-pixel area includes no electronic components for controlling the first OLED.

3. A system for emitting light comprising:

pixel structure of an organic light emitting diode (OLED) device, comprising:

a first sub-pixel area including a first OLED;

a second sub-pixel area including a second OLED and a second control circuit, wherein said second control circuit includes electronic components for controlling the second OLED, and controlling any of the first OLED, the third OLED, the fourth OLED, or a combination of the first, third and fourth OLEDs;

a third sub-pixel area including a third OLED; and

a fourth sub-pixel area including a fourth OLED.

4. The system as claimed inclaim 3, wherein the first sub-pixel area is a red sub-pixel area, green sub-pixel area, or blue sub-pixel area, and the second sub-pixel area is a white sub-pixel area.

5. The system as claimed inclaim 3, wherein the first sub-pixel area includes no electronic components.

6. The system as claimed inclaim 3, wherein said second control circuit includes electronic components for controlling the first and second OLEDs.

7. The system as claimed inclaim 3, wherein said second control circuit includes electronic components for controlling the first, second, third, and fourth OLEDs.

8. The system as claimed inclaim 3, wherein the first sub-pixel area further includes a first control circuit for controlling the first OLED.

9. The system as claimed inclaim 8, wherein the first control circuit includes a switch transistor for controlling the first OLED, and wherein the second control circuit includes a capacitor and a driving transistor for controlling the first OLED.

10. The system as claimed inclaim 9, wherein the first sub-pixel area is a red sub-pixel area, green sub-pixel area, or blue sub-pixel area, and the second sub-pixel area is a white sub-pixel area.

11. The system as claimed inclaim 10, wherein the first sub-pixel area is a blue sub-pixel area.

12. The system as claimed inclaim 3, comprising:

a first sub-pixel area including a first OLED and a first control circuit for controlling the first OLED;

a second sub-pixel area including a second OLED and a second control circuit, wherein said second control circuit includes electronic components for controlling the second OLED, and controlling any one of the first OLED, the third OLED, the fourth OLED, or a combination of the first, third and fourth OLEDs;

a third sub-pixel area including a third OLED and a third control circuit for controlling the third OLED; and

a fourth sub-pixel area including a fourth OLED and a fourth control circuit for controlling the fourth OLED.

13. The system as claimed inclaim 12, wherein the first sub-pixel area is a red sub-pixel area, green sub-pixel area, or blue sub-pixel area, and the second sub-pixel area is a white sub-pixel area.

14. The system as claimed inclaim 12, wherein said second control circuit includes electronic components for controlling the first and second OLEDs.

15. The system as claimed inclaim 12, wherein said second control circuit includes electronic components for controlling the first, second, third, and fourth OLEDs.

16. The system as claimed inclaim 1, wherein:

the system further comprises a display device; and

the pixel structure forms a portion of the display device.

17. The system as claimed inclaim 16, wherein:

the system further comprises an electronic device comprising the display device.

18. The system as claimed inclaim 16, further comprising a controller coupled to the display device to render an image to be displayed by the display device.

19. The system as claimed inclaim 16, further comprising means for rendering an image to be displayed by the display device.

20. A system for emitting light comprising:

an electronic device having a display device, the display device being operative to display images;

the display device comprising pixels, at least one of which comprises:

a first sub-pixel area including a first OLED; and

a second sub-pixel area including a second OLED and a second control circuit, wherein said second control circuit includes electronic components for controlling said first and second OLEDs.

Images